Nonlinear magnetohydrodynamic modeling of ideal ballooning modes in high-$β$ Wendelstein 7-X plasmas

Fuente: arXiv
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Autores principales: Zhou, Yao, Aleynikova, K., Liu, Chang, Ferraro, N. M.
Formato: Preprint
Publicado: 2026
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author Zhou, Yao
Aleynikova, K.
Liu, Chang
Ferraro, N. M.
author_facet Zhou, Yao
Aleynikova, K.
Liu, Chang
Ferraro, N. M.
contents We present nonlinear magnetohydrodynamic (MHD) simulations of high-$β$ Wendelstein 7-X plasmas using the stellarator extension of the M3D-$C^1$ code, building on the recent work that shows benign saturation of ideal ballooning modes above the designed $β$ limit in the standard configuration [Y. Zhou et al, Phys. Rev. Lett. 133, 135102 (2024)]. First, we examine the results' sensitivity to the parallel thermal conductivity. It is found that while an increased parallel conductivity reduces the linear growth rate, the saturated pressure profile is barely affected. Second, we consider the dependence on the profile shape. It is shown that an equilibrium with a peaked pressure profile and lower $β$ is subject to more significant change than a broad profile with higher $β$ and a larger growth rate, suggesting that benign saturation, or nonlinear stability, is not guaranteed and not dictated by linear growth. Third, we study the influence of the magnetic configuration, with the equilibrium rotational transform varied by adjusting the planar coil current. With similar growth rates, similar magnitudes of profile change are found regardless of the presence of a low-order resonance, which implies that the saturation mechanism is not specific to a resonant or non-resonant mode. These results indicate that MHD stability should still be treated seriously in stellarator operation and design, for which nonlinear modeling using tools like M3D-$C^1$ can play an instrumental role.
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id arxiv_https___arxiv_org_abs_2603_00869
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Nonlinear magnetohydrodynamic modeling of ideal ballooning modes in high-$β$ Wendelstein 7-X plasmas
Zhou, Yao
Aleynikova, K.
Liu, Chang
Ferraro, N. M.
Plasma Physics
We present nonlinear magnetohydrodynamic (MHD) simulations of high-$β$ Wendelstein 7-X plasmas using the stellarator extension of the M3D-$C^1$ code, building on the recent work that shows benign saturation of ideal ballooning modes above the designed $β$ limit in the standard configuration [Y. Zhou et al, Phys. Rev. Lett. 133, 135102 (2024)]. First, we examine the results' sensitivity to the parallel thermal conductivity. It is found that while an increased parallel conductivity reduces the linear growth rate, the saturated pressure profile is barely affected. Second, we consider the dependence on the profile shape. It is shown that an equilibrium with a peaked pressure profile and lower $β$ is subject to more significant change than a broad profile with higher $β$ and a larger growth rate, suggesting that benign saturation, or nonlinear stability, is not guaranteed and not dictated by linear growth. Third, we study the influence of the magnetic configuration, with the equilibrium rotational transform varied by adjusting the planar coil current. With similar growth rates, similar magnitudes of profile change are found regardless of the presence of a low-order resonance, which implies that the saturation mechanism is not specific to a resonant or non-resonant mode. These results indicate that MHD stability should still be treated seriously in stellarator operation and design, for which nonlinear modeling using tools like M3D-$C^1$ can play an instrumental role.
title Nonlinear magnetohydrodynamic modeling of ideal ballooning modes in high-$β$ Wendelstein 7-X plasmas
topic Plasma Physics
url https://arxiv.org/abs/2603.00869